A synonym for a load sensing system is the concept of a load pressure reporting system. The system is a hydraulic control system with pressure and volumetric flow matching, specifically to the instantaneous requirements of one or more consumers. Commercially common load sensing systems can be implemented both with a fixed displacement pump and with an adjustable displacement pump.
In hydraulic systems and controls, the individual consumers can be arranged in series and/or parallel to one another in the supply circuit.
In a conventional series connection, the same liquid stream flows through the individual consumers, and the pressures are added to one another. The return of one consumer forms the inflow of the next consumer so that the entire volumetric flow is available to each consumer in succession. The series connection is used especially wherever consumers with low load pressures are present.
The velocity of the consumers is controlled independently of the load pressure, preferably via proportional flow regulators comprising a proportional choke valve and a bypass manometric balance. In this arrangement, the velocities of the two consumers can be set independently of one another, which is a good idea for a plurality of applications.
Consumers connected in parallel conversely are all subject to the same input pressure and volumetric flows. To operate all consumers at the same time with maximum velocity, the supply pump must be dimensioned to be correspondingly large, which is not necessary in a series connection, as shown.
In a load sensing system of this type, the highest load pressure is determined and the pump pressure is raised by a certain amount over this load pressure, for example, by a circulation manometric balance. In a system including a combination of parallel and series connections, a pressure higher than is necessary for the series connection section cannot build up, since there the excess fluid (oil) is routed to the tank via the bypass manometric balances. This bypass arrangement is especially undesirable when higher pressures are needed in the parallel section, for example, to be able to ensure operation of a machine and its parts.